One advantage of a numeral lock is that it can unlocked without a key. A numeral lock can be used by many people at the same time who need not be inconvenienced by carrying a key. Some prior art numeral locks have only one combination which cannot be changed. Thus, the numeral lock must be discarded if the combination is disclosed to an unauthorized user.
There still remains a need for a numeral lock with a plurality of sets of unlocking numbers which are changeable at will.